[lammps-users] [Help] The real meaning of pxx pyy pzz

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1

Hi,

I cut a bulk nickel for about 800 atoms, by using PBC along x, y and z direction and EAM potential. Then I optimized the crystalline by using minimize command, and calculated pxx, pyy, pzz. Naturally, a crystalline should have no internal stress. The expected value of pxx, pyy and pzz should approximate to 0. However, the pxx, pyy and pzz I obtained is around -3058.5585 bar.

I wander what is the real meaning of pxx, pyy, pzz. Does they mean the stress of the corresponding direction (x, y and z)?

Thanks a lot!

2

Pxx is the xx component of the pressure tensor. If you
created atoms on a perfect lattice, a minimization shouldn't
do anything, so I'm not clear what you're after. The pressure
should only be a function of the lattice constant. If that's not
what you expect, that that's the potential, not LAMMPS.

Steve